U.S. patent application number 10/197191 was filed with the patent office on 2002-12-05 for implantable defibrillator with wireless vascular stent electrodes.
Invention is credited to Beutler, Arthur J., Bulkes, Cherik, Denker, Stephen.
Application Number | 20020183791 10/197191 |
Document ID | / |
Family ID | 25060624 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020183791 |
Kind Code |
A1 |
Denker, Stephen ; et
al. |
December 5, 2002 |
Implantable defibrillator with wireless vascular stent
electrodes
Abstract
A cardiac defibrillator includes a fibrillation detector, which
determines when a medical patient requires defibrillation at which
time a transmitter produces a radio frequency signal. A first stent
electrode is implanted into a blood vessel at a first location in
the medical patient and a second stent electrode is implanted into
a blood vessel at a second location. The first stent electrode
contains an electronic circuit that is electrically connected to
the second stent electrode. In response to receiving the radio
frequency signal, the electronic circuit uses energy from that
signal to apply an electric defibrillation pulse between the first
and second stent electrodes.
Inventors: |
Denker, Stephen; (Mequon,
WI) ; Bulkes, Cherik; (Sussex, WI) ; Beutler,
Arthur J.; (Greendale, WI) |
Correspondence
Address: |
QUARLES & BRADY LLP
411 E. WISCONSIN AVENUE
SUITE 2040
MILWAUKEE
WI
53202-4497
US
|
Family ID: |
25060624 |
Appl. No.: |
10/197191 |
Filed: |
July 17, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10197191 |
Jul 17, 2002 |
|
|
|
09760936 |
Jan 16, 2001 |
|
|
|
6445953 |
|
|
|
|
Current U.S.
Class: |
607/5 |
Current CPC
Class: |
A61N 1/37223 20130101;
A61N 1/37211 20130101 |
Class at
Publication: |
607/5 |
International
Class: |
A61N 001/39 |
Claims
We claim:
1. A cardiac defibrillator, for implantation into a medical
patient, comprises: a control circuit having a fibrillation
detector to determine when the medical patient requires
defibrillation, and a transmitter to produce a radio frequency
signal at a given frequency in response to the fibrillation
detector; a first stent electrode for implantation into a blood
vessel at a first location in the medical patient; a second stent
electrode for implantation into a blood vessel at a second location
in the medical patient; and an electronic circuit mounted to the
first stent electrode and electrically connected to the second
stent electrode, wherein upon receipt of the radio frequency
signal, the electronic circuit applies an electric defibrillation
pulse between the first stent electrode and the second stent
electrode.
2. The apparatus as recited in claim 1 wherein the electronic
circuit comprises: an antenna for receiving the radio frequency
signal; a detector connected to the antenna and tuned to the given
frequency of the radio frequency signal and; an electrical storage
device connected to the detector and storing electrical energy from
the radio frequency signal; and a discharge circuit which applies
electrical energy from the electrical storage device to the first
stent electrode and the second stent electrode.
3. The apparatus as recited in claim 2 wherein the electrical
storage device is a capacitor.
4. The apparatus as recited in claim 1 wherein the electronic
circuit comprises: an antenna for receiving the radio frequency
signal; a detector connected to the antenna and tuned to the given
frequency of the radio frequency signal and; a capacitor; a
charging circuit connected to the detector and the capacitor, and
applying electrical energy derived from the radio frequency signal
to produce a voltage across the capacitor; and a discharge circuit
which applies the voltage across the capacitor to the first stent
electrode and the second stent electrode.
5. The apparatus as recited in claim 1 wherein the first stent
electrode is expandable within the blood vessel from a first
cross-sectional size to a second cross-sectional size.
6. The apparatus as recited in claim 1 wherein the second stent
electrode is expandable within the blood vessel from a first
cross-sectional size to a second cross-sectional size.
7. The apparatus as recited in claim 1 further comprising a third
electrode for implantation into a blood vessel in the medical
patient and connected to the electronic circuit, wherein the
electric defibrillation pulse also is applied across the first
stent electrode and the third stent electrode.
8. A cardiac defibrillator, for a medical patient, comprising: a
fibrillation detector, which determines when the medical patient
requires defibrillation and produces a control signal; a
transmitter connected to the fibrillation detector to produce a
radio frequency signal and to transmit the control signal; a first
stent electrode for implantation into a blood vessel at a first
location in the medical patient; a second stent electrode for
implantation into a blood vessel at a second location in the
medical patient; and an electronic circuit mounted to the first
stent electrode and electrically connected to the second stent
electrode, the electronic circuit storing energy received from the
radio frequency signal and in response to the control signal
employing the stored energy to apply an electric defibrillation
pulse across the first stent electrode and the second stent
electrode.
9. The apparatus as recited in claim 8 further comprising a third
electrode for implantation into a blood vessel in the medical
patient with connection to the electronic circuit, wherein the
electric defibrillation pulse also is applied across the first
stent electrode and the third stent electrode.
10. The apparatus as recited in claim 8 wherein the electronic
circuit comprises: a detector tuned to the given frequency of the
radio frequency signal; a capacitor; a charging circuit connected
to the detector and the capacitor, and applying electrical energy
derived from the radio frequency signal to produce a voltage across
the capacitor; and a discharge circuit which in response to the
control signal applies the voltage across the capacitor to the
first stent electrode and the second stent electrode.
11. A method for defibrillating a heart of a medical patient, the
method comprising: implanting a first stent electrode into a blood
vessel at a first location in the medical patient, the first stent
electrode having an electronic circuit; implanting a second stent
electrode into a blood vessel at a second location in the medical
patient, wherein second stent electrode is connected to the
electronic circuit of the first stent electrode; detecting when
defibrillation of the heart is required; in response to detecting
when defibrillation of the heart is required, transmitting a
wireless signal to the electronic circuit of the first stent
electrode; and in response to receipt of the wireless signal, the
electronic circuit applying a voltage across the first stent
electrode and the second stent electrode.
12. The method as recited in claim 11 further comprising: charging
a capacitor using energy from the wireless signal; and discharging
the capacitor to applying the voltage across the first stent
electrode and the second stent electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/760,936 filed Jan. 16, 2001.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to implantable medical devices
which deliver energy to cardiac tissue for the purpose of
maintaining or producing a regular heart rate. Such devices are
commonly referred to as cardiac pacing devices and
defibrillators.
[0005] 2. Description of the Related Art
[0006] A remedy for people with slowed or disrupted natural heart
beating is to implant a cardiac pacing device. A cardiac pacing
device is a small electronic apparatus that stimulates the heart to
beat at regular rates. It consists of a pulse generator, implanted
in the patient's chest, which produces electrical pulses to
stimulate heart contractions. Electrical leads extend from the
pulse generator to electrodes placed adjacent to specific muscles
of the heart, which when electrically stimulated produce
contraction of the adjacent heart chambers.
[0007] Modern cardiac pacing devices adapt their pulse rate to
adjust the heartbeats to the patient's level of activity, thereby
mimicking the heart's natural beating. The pulse generator modifies
that rate by tracking the activity at the sinus node of the heart
or by responding to other sensors that monitor body motion and rate
of breathing.
[0008] Different pacing needs are met by adjusting the programming
of the pulse generator and by the location of the electrodes. It is
quite common that the leads extend through blood vessels which
enter the heart so that the electrodes can be placed in the muscle
of the heart chamber requiring stimulation. This requires that the
leads extend for some distance through the blood vessels and may
necessitate that the leads pass through one or two heart valves. In
other patients, patch electrodes are placed on the exterior heart
surface with wires extending through tissue to the pacing device.
With either type of lead placement, it is important that the
electrodes be attached to the proper positions on the heart to
stimulate the muscles and produce contractions. Thus it is
desirable to properly locate the electrodes for maximum heart
stimulation with minimal adverse impact to other physiological
functions, such as blood circulation.
[0009] Other patients have hearts that occasionally go into
fibrillation where the heart has very rapid shallow contractions
and, in the case of ventricular fibrillation, may not pump a
sufficient amount of blood to sustain life. Administration of a
controlled electrical shock to the heart often is required to
restore a normal rhythm. A defibrillator often is implanted in the
chest cavity of a person who is susceptible to reoccurring episodes
of ventricular fibrillation. Similar to a pacing device, the
implanted defibrillator senses the rapid heart rate during
fibrillation and applies a relatively high energy electrical pulse
through wires connected to electrodes attached to the exterior wall
of the heart. The defibrillator generates a much more intense
electrical pulse than is used by pacing devices which merely
stimulate contractions of the heart.
SUMMARY OF THE INVENTION
[0010] cardiac defibrillator includes a control circuit that has a
fibrillation detector, which determines when a medical patient
requires defibrillation. A transmitter produces a radio frequency
signal at a given frequency in response to the fibrillation
detector determining that defibrillation is required. A first stent
electrode and a second electrode are provided for implantation into
blood vessels at different locations in the medical patient. For
example, the first stent electrode and a second electrode are to be
implanted on different sides of the patient's heart.
[0011] An electronic circuit is mounted to the first stent
electrode and electrically connected to the second stent electrode.
Upon receipt of the radio frequency signal, the electronic circuit
applies an electric defibrillation pulse between the first stent
electrode and the second stent electrode.
[0012] In the preferred embodiment, the electronic circuit contains
an RF detector that is tuned to receive the radio frequency signal.
A charging circuit employs energy from the radio frequency signal
received by the RF detector to charge a capacitor which acts as an
electrical storage device. A discharge circuit responds to the
control signal by applying the stored energy from the capacitor to
the first and second stent electrodes, thereby producing a
defibrillation pulse across the patient's heart.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic representation of a cardiac pacing
device implanted in a medical patient;
[0014] FIG. 2 is a circuit diagram of the pacing device in FIG.
1;
[0015] FIG. 3 is an isometric cut-away view of a cardiac blood
vessel with a vascular electrode-stent;
[0016] FIG. 4 is a block diagram of an electrical circuit on the
vascular electrode-stent;
[0017] FIG. 5 is a representation of an implanted defibrillator
employing vascular stent electrodes;
[0018] FIG. 6 is a block diagram of a defibrillator control circuit
in FIG. 5; and
[0019] FIG. 7 is a block diagram of a defibrillator pulsing circuit
on a vascular stent.
DETAILED DESCRIPTION OF THE INVENTION
[0020] With initial reference to FIG. 1, an apparatus for applying
electrical stimulation to pace a heart 10 comprises a pacing device
12 and one or more vascular electrode-stents located in arteries 14
which supply blood to the heart muscles. As will be described in
greater detail, the pacing device 12 emits a radio frequency signal
16 which produces an electric current in the implanted vascular
electrode-stent thereby stimulating the heart muscle.
[0021] Referring to FIG. 2, the pacing device 12 comprises a
conventional pacing signal generator 20 similar to that utilized in
previous cardiac pacers that use electrodes connected to leads. The
internal circuitry and operation of the pacing signal generator is
similar to those prior cardiac pacers. However, instead of the
output stimulation signals being applied to the electrodes via
leads, the pacing signals are applied to an input of a radio
frequency (RF) transmitter 22. Both the pacing signal generator 20
and the RF transmitter 22 are powered by a battery (not shown). In
response to the stimulation signal (also known as a pacing signal)
from the generator 20, the radio frequency transmitter 22 generates
a correspondingly long pulse of the radio frequency signal 16 that
is transmitted throughout the chest cavity via an antenna 24.
Preferably the antenna 24 either is located relatively close to the
heart or is of a type which focuses the radio frequency signal
toward the heart.
[0022] FIG. 3 illustrates an electrode-stent 30 that is placed in a
blood vessel 14 of the heart 10. The body 33 of the electrode-stent
30 has a design similar to well-known expandable vascular stents
that are employed to enlarge a restricted vein or artery. Such
vascular stents have a generally tubular design that initially is
collapsed to a relatively small diameter enabling them to pass
freely through an blood vessel of a patient.
[0023] The procedure for implanting the electrode-stent 30 is
similar to that used for conventional vascular stents. For example,
the balloon at the end of a standard catheter is inserted into the
electrode-stent 30 in a collapsed, or reduced diameter,
configuration. That assembly then is inserted through an incision
in a vein or artery near the skin of a patient and pushed through
the vascular system to the appropriate location adjacent the heart
10. Specifically, the electrode-stent 30 ultimately is positioned
in a cardiac blood vessel 14 adjacent to a section of the heart
muscle where stimulation should be applied. The balloon of the
catheter then is inflated to expand the vascular electrode-stent
30, thereby slightly enlarging the blood vessel 14 which embeds the
electrode-stent 30 in the wall of the vein or artery, as seen in
FIG. 3. This slight enlargement of the blood vessel and the tubular
design of the electrode-stent allows blood to flow relatively
unimpeded through the device. The balloon is deflated, the catheter
is removed from the patient, and the incision is closed. The
electrode-stent 30 remains in the blood vessel without any wire
connecting an electrode to pacing device 12. Alternatively a
self-expanding stent may be utilized.
[0024] With reference to FIGS. 3 and 4, the vascular
electrode-stent 30 has a body 33 on which is mounted a signal
receiving circuit 32. The signal receiving circuit 32 includes an
antenna 34, a radio frequency signal detector 36, and a stimulator,
that is formed by first and second electrodes 38 and 40, for
example. The antenna 34 is connected to an input of the radio
frequency signal detector 36. That detector is tuned to the
frequency of the RF signal 16 that is emitted by the pacing device
12. Upon detecting the radio frequency signal 16, the detector 36
converts the energy of that signal into an electric current that is
applied to the first and second electrodes 38 and 40. Those
electrodes form an electric circuit path with the patient's heart
tissue allowing for stimulation of that tissue. Thus, each time the
pacing device 12 emits a radio frequency signal 16, a pulse of
electrical current is produced in the vicinity of the
electrode-stent 30, thereby stimulating the heart muscle adjacent
to that electrode.
[0025] Therefore, instead of coupling the pacing device to the
electrodes by wires extending through the vascular system and even
the heart itself, the present invention employs radio frequency
signals to provide that coupling. This eliminates the need for
electrical leads that extend through the blood vessels which can
break thus disabling the cardiac pacing. Furthermore, the present
electrode-stents 30 and 31 can be located in the cardiac blood
vessels 14 at points that are directly associated with the specific
muscles requiring stimulation.
[0026] With reference to FIG. 1, a plurality of vascular
electrode-stents 30 and 31 which are tuned to the same radio
frequency can be positioned in cardiac blood vessels at different
locations in the heart to provide simultaneous stimulation of the
adjacent tissue regions.
[0027] Alternatively, the plurality of electrode-stents 30 and 31,
implanted in various veins or arteries of the heart muscle, can be
tuned to different radio frequencies. In this embodiment, the radio
frequency transmitter 22 also is tunable to produce output signals
at several different radio frequencies, in response to an
electrical control signal from the pacing signal generator 20. The
pacing signal generator 20 now specifies the duration and the
frequency of the RF signal 16 in order to select an electrode-stent
to stimulate the heart muscle at a particular location. As a
consequence, different portions of the heart muscle can be
stimulated independently and sequentially by varying the radio
frequency of the emitted signal 16 to correspond to the frequency
to which the electrode-stent 30 in a given location is tuned.
Furthermore, the plurality of electrode-stents 30 can be activated
in a given sequence by producing a series of pacer signals at
different radio frequencies. This enables the pacing device 12 to
produce a sequential contraction of the heart chambers to increase
cardiac efficiency.
[0028] Electrode stents also can be employed with a cardiac
defibrillator 50 as illustrated in FIG. 5. The defibrillator 50 has
a control circuit 51 which detects fibrillation of the heart via
sensor 49 and sends a radio frequency control signal to a primary
electrode stent 52 located in a vein or artery 54 in one section of
the heart. The primary electrode stent 52 includes the electronic
circuitry 54 for the defibrillator 50 and a first electrode 55. The
electronic circuitry 54 is connected to a secondary electrode stent
58 by a wire 56 that extends through the vascular system. The
secondary electrode stent 58 is located in another blood vessel 59
in a different section of the heart and has a second electrode 57
to which the wire 56 is attached. Additional secondary electrode
stents 60 and 62 can be placed into other veins or arteries 59 of
the heart. These other secondary electrode stents 60 and 62 have a
structure identical to secondary electrode stent 58 with third and
fourth electrodes 64 and 66 connected by wires to the primary
electrode stent 52. The primary and secondary electrode stents 52,
58, 60 and 62 are implanted using a procedure similar to that
described previously for electrode stent 30. The secondary
electrode stents 52, 58, 60 and 62 may be significantly smaller
that the primary electrode stent 52 as they do not contain
electronic circuitry, such as a charge storage capacitor as will be
described. Thus the secondary electrode stents can be placed in
smaller blood vessels.
[0029] With reference to FIG. 6, the defibrillator control circuit
51 preferably is implanted in the chest of the patient, but may be
worn externally in close proximity to the heart. The control
circuit 51 has a fibrillation detector 70 which employs
conventional techniques to detect an irregular heart rate and
determine when a defibrillation pulse should be applied to the
patient's heart. When that is to occur, the fibrillation detector
70 signals the radio frequency (RF) transmitter 72 to send a
wireless signal via antenna 76 to the primary electrode stent 52.
The resultant radio frequency signal has greater energy than the
signal from the pacing circuit 12 in FIG. 2 and thus provides
sufficient energy to enable the primary electrode stent 52 to
deliver a more intense defibrillation pulse to the patient. A
battery 74 provides power for the control circuit 51.
[0030] Referring to FIG. 7, the electronic circuitry 54 on the
primary electrode stent 52 includes an antenna 80 for receiving the
radio frequency signal from the control circuit 51. An RF detector
82 is tuned to the designated radio frequency and applies energy
from the received signal to a charging circuit 84. The charging
circuit 84 uses the signal energy to charge a capacitor 85. When
the charge on the capacitor is sufficient to produce a
defibrillation pulse, a discharge circuit 86 dumps the charge to
the electrode 55 on the primary electrode stent 52. The electrodes
57, 64 and 66 of the secondary electrode stents 58, 60 and 62 are
connected by wires to the primary electrode stent 52 thereby
providing an return pole to complete an electrical circuit for the
charge pulse. This action applies an electrical pulse across the
first electrode 55 and the second, third and fourth electrodes 57,
64 and 66 which shocks the patient's heart to restore a normal
cardiac rhythm. Employing a plurality of secondary electrode stents
58, 60 and 62 to form a circuit to the primary stent provides a
greater dispersion of the energy and avoids a local discharge.
[0031] The radio frequency signal from the control circuit 51 has a
duration that is sufficient to charge the capacitor 85 to the level
necessary to deliver the electrical defibrillation pulse.
Alternatively, the control circuit 51 may periodically send a brief
radio frequency signal to the electronic circuitry 54 on the
primary electrode stent 52. This signal does not cause the stent
circuitry to deliver a defibrillation pulse, but is used merely to
maintain the requisite charge on the capacitor 85. This ensures
that the capacitor 85 will be nearly fully charged when a
defibrillation pulse is required and shortens the time between
receipt of the defibrillation signal and delivery of an electrical
pulse to the heart. In this latter case the RF transmitter 72 sends
a specially encoded control signal when the patient requires
defibrillation. The RF detector 82 responds to that encoded control
signal by triggering the discharge circuit 86 to deliver the
electrical defibrillation pulse.
[0032] The foregoing description was primarily directed to a
preferred embodiments of the invention. Even though some attention
was given to various alternatives within the scope of the
invention, it is anticipated that one skilled in the art will
likely realize additional alternatives that are now apparent from
disclosure of embodiments of the invention. Accordingly, the scope
of the invention should be determined from the following claims and
not limited by the above disclosure.
* * * * *